Subcutaneous structures and blood vessels under skin are barely visible for naked eyes. In order to identify and locate the subcutaneous structures and blood vessels, medical doctors have to rely on the external outline of human body and their anatomic knowledge.
The blood vessels, including veins and arteries, are below the epidermis, and even covered by subcutaneous fat. Visible light imaging signals, reflected back from subcutaneous structures and blood vessels under the visible light illumination, are extremely faint and mixed with scattered light and various phantoms. Before puncturing, in order to make the blood vessels more visible, medical doctors often ask patients to clench their fists or flap the skin above the blood vessel. However, hindered by ages, or thickness of subcutaneous fat of patients etc., the visibility of subcutaneous blood vessels is still not satisfied in most cases. Injection relying on the vague images of blood vessels often results misalignment of the puncture, causing pain in patients, delaying optimal time for medical treatments, and even triggering injection incident.
In addition to drawing blood and injections in various occasions, blood vessels are also needed to be accurately located during acupuncture and medical surgeries.
An existing vein image enhancer, projects the obtained near-infrared (NIR) image of the venous blood vessels, by the visible light, directly onto the skin surface of a human body. In order to reduce the alignment errors, the existing vein image enhancer uses complex optical system, including complex mechanical servo mechanism, for ensuring the infrared imaging and the visible light projection being aligned in the same optical axis. Therefore, the design of the complex optical system will lead to enormous volume, heavy weight and huge power consumption, which is not suitable for mobile medical diagnosis and other portal applications.